Reference

How players are compared

Every comparison in this notebook is a preregistered match between two named players on identical seeds, scored by effective win rate with a 95% interval. The rules of the match, the players and the decision rule are frozen in experiments/<uuid>.toml before a game is played.

Paired seeds

A match of n games uses n / 2 seeds. Each seed is played twice, once with each player as Red, so that both sides see the same random setups and the same tie-breaking randomness. The per-seed contrast (the candidate's score as Red plus its score as Blue, minus one) is the unit of analysis for paired experiments, and the reported interval is over seeds. Red moves first; the Ataraxos self-play returns for Red and Blue were roughly equal, which supports the human belief that move priority is not strategically significant, but pairing removes the question from the comparison.

Effective win rate

A win counts one, a draw a half, a loss zero, following the scoring of the Ataraxos evaluation series. The record reports wins, draws and losses separately beside the effective rate, and the endings histogram (flag captured, no legal moves, both immobile, battleless-move limit, length limit, resignation) so a policy that wins by stalling is visible.

The 95% interval on a proportion is the Wilson score interval. For a paired contrast it is the normal-approximation interval over seeds. Neither is a significance test; the decision rule of each registration says what the interval has to exclude.

Rules presets

training is the paper's training configuration: a draw after 100 consecutive battleless moves and after 4,000 moves. competitive uses the 200-move rule of the Strategus platform. Both enforce the two-square rule and the continuous-chase rule. A registration names its preset; results under different presets are not pooled.

Elo and its caveats

Round-robin tournaments report Elo fitted from pairwise scores, anchored at 1000 for random. The Ataraxos paper warns that Elo in Stratego is useful but flawed because randomisation compresses margins: two players can be closer to each other than their margins against a common third player predict. Elo here orders the ladder; promotion decisions use the paired contrast against the previous rung, never an Elo difference.

Information boundary

A policy receives its own Observation and the legal moves computed by the arbiter. The observation carries the public anti-chase trackers so that a searcher can rebuild rule-exact states, but never a hidden type, the arbiter's Zobrist key or the random seed. Search-based players sample hidden pieces from the observation alone. The training environment does expose hidden types, as belief targets, to the learner only.

What counts as support

A candidate is promoted when the preregistered interval on the paired contrast against the previous rung excludes zero in its favour on the full game count, and any cost constraint in the registration holds (time per move, memory). A run stopped early, an interval overlapping zero, or a result on a smoke preset is recorded and not promoted.